Dana - False Corner / Flare question

[D-MAN]

None of that is really critical, remember, the real Khorn has a giant cutout on the tailboard for baseboard heaters! So much for an even expansion rate!

But I agree, using the Khorn as a model is a fine example of how to accomplish certain things, with a known and expected outcome.

Dana

[D-MAN]

Let's talk "WINGS".

As seen in the 1945 Khorn patent, the original Khorn had pronounced "wings". There is a rich tradition for this, for instance PWK's first corner horn 1943 corner horn patent.

The general idea is to keep the horn pathway "under pressure" for the longest possible or practical length.

However, in the 50's, the Khorn developed into the version we see today, the wings are "clipped" back and the horn starts to unload "early" (or not, as we will see).

Attached is the 1943 patent with the traditional extended "wings".

[D-MAN]

Although I can't seem to find it currently on the USPTO site, the 1950's (?) PWK design patent on the Khorn (as we are familiar with) appearance has a cut-back top with no extended "wings" per se. The patent # in question will be on your Khorn label starting with a "D"... if I had it handy, I'd attempt to post it here.

Now, if it mattered to the sound, why would PWK cut it back just to make it look better (or sell more due to a higher WAF)? Well, the answer is that it doesn't matter...

Many corner honr speakers featured "wings", especially the bifurcated ones. But then there's the EV Aristocrats, Centurions, ect., licensed under Klipsch patents. No tailboard!
No wings! What?!

For example, the Klipsch licensed EV Aristocrat... (or Klipsch Shorthorn/Rebel)

DM

[D-MAN]

Another Klipsch design without a tailboard and cut back "wings"... the original Shorthorn patent...

[D-MAN]

Another little-known example of a bifurcated corner horn with no tailboard and cut-back exit channels ala Khorn is the EV Centurion...

The point of all this is to explain the following:

1) there are plenty of examples of commercially viable horns with no tailboards - i.e., tailboards are NOT required to have good low frequency reponse.

2) Keeping the horn channels confined for the longest possible pathway length is NOT required for good low frequency response.

3) Both of the above is due to corner placement.

4) the Khorn has undergone various changes over the years, with the 1946 model (as posted by Armando) being the most technically advanced, i.e., it incorporated many of the possible enhancements seemingly without regard for economic concerns.

[D-MAN]

The 1946 12" field-coil driver version of the Khorn (plans posted by Armando previously).

Fine example of a fully-tricked out Khorn. If I was building a pair, they would have these mods in them!

DM

[D-MAN]

I should add that the old and new versions of the SL-K have 2 of the mods seen above, that is, the removable motor board and the back-chamber reinforcements.

The only 2 missing in the SL's (missing in the modern Khorn, too) is the 45 deg. splitters at the tailboard and the extended wings on the top. Add those mods and now yer-a-talkin' a full-dress bass horn!

I find it interesting that PWK left the rear splitters out of the 1945 patent, but included it in the 1943 patent, although not a full channel version! Wonder why...

DM

[tigerwoodKhorns]

I should add that the old and new versions of the SL-K have 2 of the mods seen above, that is, the removable motor board and the back-chamber reinforcements.

The only 2 missing in the SL's (missing in the modern Khorn, too) is the 45 deg. splitters at the tailboard and the extended wings on the top. Add those mods and now yer-a-talkin' a full-dress bass horn!

I find it interesting that PWK left the rear splitters out of the 1945 patent, but included it in the 1943 patent, although not a full channel version! Wonder why...

DM

If I add the splitters, do I move the tail board back or leave as is (3.5" from speaker exit)?

I see your point with the extensions but I am building false corners in a more compact design (still too big to pass the WAF) so that I can place them like regular speakers. I enjoyed my old K Horns the most when I could move them around and toe in as I saw fit. They became like a regular speaker and it was nice.

Chris

[D-MAN]

3-3/4" to 4" would be my choice, but we are splitting hairs now. Non-exansion (3-1/2") is also pefectly acceptable.

The side exit channels for maintaining the expansion at the narrowest should be no narrower than 3-3/4" (4" would be fine). It doesn't demand alot of precision at this point in the horn, that little variance will not change the flare rate, but 1/4" difference is far less variance to the overall channel proportions than the traditional Khorn tailboard/baseboard cutouts, etc., so you see what I mean...

Now for those who will torture themselves over something like a 1/4" variance in the terminal horn channels, I would say this: your baseboards along the walls (different in every house) cause far more channel volume variations - yet it seems perfectly ok, doesn't it! PWK said that 1/2" variance in overall width was acceptable at the mouth (it's the throat area that is particularily sensitive to variations).

1/2" x 2 x 37.5" that means - OMG! that a 39 sq. in difference at the mouth (675 sq. inches)! That is the same as the 3x13" throat opening slot used in the Khorn, for an example. Do you think you can hear a difference if that size was added to the Khorn exits? Not likely and its not likely that there would be a measurable

Frankly, the Khorn could use the extra area (at 675 sq. inches) is far below the math results (Keele results, 1031 sq. in.) for an optimum 1/8 space horn houth!

Which begs the question - where EXACTLY is the Khorn mouth? Evidence is pointing to the fact that it actually exists somewhere beyond the horn terminus proper, because its frequency response is certainly measurable at 40Hz, but the "apparent" combined mouth size is too small to accomplish that response according to theory!

DM

[3dzapper]

That's thought provoking DM. Where does the corner's horn loading transfer to room loading?

An answer may lie in PWK's 4x4 foot false corners. If true, that would give a mouth of 60x48 or 2,880sqin. I would assume it to be in the middle somewhere.

Does that work?

Rick

[tigerwoodKhorns]

That's thought provoking DM. Where does the corner's horn loading transfer to room loading?

An answer may lie in PWK's 4x4 foot false corners. If true, that would give a mouth of 60x48 or 2,880sqin. I would assume it to be in the middle somewhere.

Does that work?

Rick

PWK's 4' x 4' design was based on the width of a sheet of plywood. No hidden meaning or truth to be found, just the width of a sheet of wood.

[WMcD]

There may be a technical explanation for the lack of wings. They certainly extend the length of the bass horn by, say, 10 inches and also therefore increase the mouth size. This would be considered to be good.

However, they may be creating another problem. The mouth is now farther away from the corner.

Following Keele, the room corner can be modeled as a conical section. The condition there is that bass loading for the conical section is best with the smallest possible (relatively) throat, which means there would be no cabinet and the exponential horn is built into the other room. One of the old masters had drawing. I posted the article.

Let me clear that up a bit. With a conical expansion, the closer you get to the point of the cone, the more the expansion resembles an exponential horn with a lower Fc. The conical expansion resembles a bunch of exponential horns with increasing Fc as we move away from the point, which is to say, the corner. (Note that Olson's use of graduated exponential horns actually results in a conical horn.)

So, by removing the wings, we may be effectively getting a smaller mouth of the bass horn (bad), but we're also getting a smaller throat of the conical section (good) of the room. The bottom line is that the change might not make much of a difference to performance, for that reason.

I've also posted some the FM-TV articles about the early days of the K-Horn (in The Caves). The design with the wings and an upper cabinet of size to match looks ungainly. The final design, sans wings, is much more trim, and marketable.

- - - -

DMan brings up some interesting points. Perhaps they can be summarized as whether the horn should be examined as reflecting surfaces, or ducts though which air flows due to pressure.

I think it works both ways because of the nature of transmission of sound in a gas. There are alternating conditons of high pressure with low volume particle velocity, and low pressure with high volume particle velocity.

Best,

Gil

[tigerwoodKhorns]

Dana and Will

Can you guys get teh answers to these questions at the Pilgrimage?

[D-MAN]

The side walls apparently keep the horn from unloading as abruptly as one might think.

Abraham Cohen attempted to explain the effect of the front baffle between the two exit channels, too. That needs to also be taken into account.

The configuration clearly works, but exactly how, I don't think that anyone knows for sure.

The Keele formula for optimum mouth size of a 40Hz 1/8th space horn is 1060 sq. inches.

PWK's formula results in 1030 sq. inches. The Khorn terminal exit size is approx. 675 sq. inches.

[3dzapper]

That's thought provoking DM. Where does the corner's horn loading transfer to room loading?

An answer may lie in PWK's 4x4 foot false corners. If true, that would give a mouth of 60x48 or 2,880sqin. I would assume it to be in the middle somewhere.

Does that work?

Rick

PWK's 4' x 4' design was based on the width of a sheet of plywood. No hidden meaning or truth to be found, just the width of a sheet of wood.

True Chris but he must have found that the coupling between the horn and the room occured within that 4' span. If it took 6' wouldn't he have specified 4'hx6'l false corners?

I have my Belles directly in front of the Khorns. Looking at them, it appears to be an extension of the corner horn's expansion. Even without the Belle, the room boundries continue the flare with the bifurcated halves combining at some point in space in front of the enclosure. If it made sense to construct an inside flare upon the front of the enclosure, I'm sure someone would have done it by now.

Your SKs have a little of that going on in the shape of the mid/high add on.

Rick

[D-MAN]

I think that if you check the size of the expansion afforded by the 48" long false corner you will find about 1000 sq. in. of area, which is right in the ball park for an optimum mouth size. I'm just guessing, but that makes sense to me in why PWK chose that particular length.

Also, this aspect of the wall-effect also expains why the apparent "lack" of full wings seems to work. Also the "no wings at all" in the case of the new-style SL-K.

DM